pgsql-bugs(at)postgresql(dot)org writes:
> postgresql=# CREATE USER mpech777;
> CREATE USER
> postgresql=# alter USER mpech777 password 'dddd';
> server closed the connection unexpectedly
Hm, it works fine here. You'll need to give more details about
platform, configuration options, any nondefault settings in
postgresql.conf, etc. A stack trace from the core dump would be
helpful as well, in case we still can't reproduce it.
regards, tom lane